Conventionally when heated water needs to be dispensed from a faucet from a hand wash basin and so forth it is usually derived from a stored location where it is pre-heated through an electrical or gas hot water system.
The problem with such arrangements is that not only do such water systems require continuous energy input to maintain the stored water at a desired temperature level, they are also by their very nature quite bulky as the water under heat needs to be initially stored within a reservoir prior to being sent across to the faucet for discharge.
As there is a storage water component as part of the arrangement it means that it often needs to be positioned away from the faucet therefore there are the associated costs and design of bringing the pipe-work from the stored water locations to the faucet for usage, which as expected often leads to measurable heat lost as well as potential water loss and so forth unless such flow on pipes are correctly kept in up to date maintenance.
More recently there has been a move towards what is known in the trade as instantaneous water heaters wherein the heating starts as soon as water enters the unit for immediate discharged from the faucet or tap.
In such arrangements incoming water into the instantaneous hot water unit is immediately heated by electric elements wherein the power to the elements is provided as soon as the water flows through the unit itself making contact with the element, wherein the heating is then withdrawn from the element as soon as the water tap is closed.
As can be seen with such instantaneous hot water heaters, energy is only consumed while water is actually flowing through the unit, advantageously therefore providing significant energy savings, as well as greater design flexibilities in that such units can be conveniently installed either within a hand wash basin or points close by therefore reducing the problems introduced above caused by withdrawing water from pipes run at a distance from stored water at a different location from the hand basin.
Arguably current instantaneous hot water heater units for low volume use, such as with hand basins and so forth, provide improvements over and above traditional hot water gas and electrical units on the basis of energy consumption, installation and flexibility of use making them suitable to be incorporated into hand basins and sinks in places such as bathrooms, restaurants, toilets, hospitals and literally any place where hand washing is required.
Nonetheless there are problems with these kinds of instantaneous hot water heater units. As introduced above for the most part many of these units operate the heating element to induce heat energy into the water by switching means that is connected directly to the operational water flow through the unit itself.
Power to the heating elements is instigated upon the operation of the faucet to discharge the flow and the unit then automatically cuts power to the heating element once discharge is complete by turning the tap off.
The person skilled in the art will appreciate that such a switching arrangement to supply power to the heating element to establish the temperature lacks any type of precision control.
The switching ON and OFF of power to the heating elements is very much mechanical and arbitrary in nature, and if some type of consistent and accurate temperature or temperature range is to be established for the discharged water improved design is required.
Under such circumstances these kinds of instantaneous hot water units as they simply provide a set power level to the heating element upon activation, are unable to differentiate between the temperature of the incoming water into the unit, and consequently the actual discharged water will be released at a proportional temperature to that of the incoming water, which has been instantaneously or immediately heated by the electrical elements.
For example conventional instantaneous hot water units in theory provide the operator the opportunity of selecting a particular temperature to which the water to be discharged from the tap or faucet should be in the range of.
Based on this desired temperature selection of the operator the heating of the electrical elements by the unit is simply driven by a current and/or voltage depending upon the magnitude of the desired temperature to that water entering the unit, upon activation of a tap or so forth.
Nonetheless no consideration is given to the actual temperature of the incoming water to the unit, so if there is a differentiation, for example water at 16° C. as opposed to water at 22° C., the discharge temperature of such water passing through these kinds of instantaneous hot water units will be substantially different, albeit for both scenarios they are expected to be the same for the end user.
Given these instantaneous hot water heater units offer such energy efficiency and by design make them so conveniently installable either above or under a sink for a hand wash basin, the fact that the actual immediate heating of the water lacks precision in actual discharged heating of the water from the outlet does raise some real concerns, and also potentially limits the application of such units for some environments.
For example many workplace, occupational health and safety standards require that outlet water temperatures do not exceed a particular threshold. Under Australian Standard AS3498-2009 for the authorisation requirements for plumbing products associated with water heaters and hot water storage tanks, temperature delivery requirements state that delivery temperature at the outlet of the appliance shall be factory set to no greater than 50° C.
As introduced above typically when the heating element is turned on when the tap is opened and water is allowed to flow therethrough, full power of the elements is applied to the water regardless of the flow rate, and regardless of the temperature of the input water.
At any given flow-rate, the amount of energy applied to water will cause the water temperature to increase by a fixed amount at that flow rate. Consequently at any given flow rate and the element power input, the difference between the inlet and outward temperatures will be constant, but the absolute value of the outlet water temperature will then depend on the inlet water temperature.
For instantaneous hot water heater units under certain flow conditions and values of incoming water temperatures, the amount of energy being applied to the water, the outlet temperature may potentially rise above maximum allowed by local standards.
Still further, if the incoming water temperature is much higher than expected, which is quite possible if the water supplied to the heating unit comes from a hot summer external environment, there is the possibility that full power to the heating element during the ON/OFF sequence of the tap or faucet could present a real risk that water discharged from the outlet presents the risk of scalding of the hands of the user.
While some instantaneous water heaters may include flow and temperature sensors linked to mechanical switches, differential pressure switches that detect when the tap is on by the pressure differential across the heater and so forth, the fact still remains that during standard factory or operational settings the unit will be designed to switch between ON and OFF cycling which will therefore introduce only full power to the heating elements thereby taking no consideration of incoming water temperature to the unit which means there is no precision or control of discharged water temperature.
Such lack of control in being able to precisely set a temperature or a temperature range of water discharged from the outlet of these instantaneous hot water heater units makes their application in places such as restaurants, hospitals, factories where workers need to continually sterilise their hands and so forth, make the use of these conventional units inappropriate at present, as such environments demand that the discharge temperature of the water from the unit not exceed a particular limit but also importantly be able to be sustained at a particular temperature for a period of time so that an operator washing his or her hand from the basin using the heater unit meets the general requirements that demand that the hand is continually washed under a certain temperature condition for a certain period of time.
While there are electro-mechanical switches which for the most part use passive components to detect changes in temperature and therefore able to open or close a contact when a specified level is reached, these switches directly activate the power being sent to the heating element without requiring an inter-connected controller or electronic circuit.
While such electro-mechanical switches may appear to provide cost effectiveness and design simplicity, it is well recognised the mechanical resistance of the individual parts often causes the switch to commute back not to the original actuating position but at a later release position introducing hysteresis into the control and thereby the ability to accurately detect a small temperature change so as to provide the necessary ON and OFF sequence to the heating element to generate and sustain water at a particular set temperature or range.
It is well recognised also that electro-mechanical switches move gradually from their initial position to actuating position and on to its final position and vice versa hence there are real transition zones in the turning ON and OFF of the power to the heating element of the instantaneous hot water heater unit, again leading to severe deficiencies in the accuracy and precision of being able to sustain and limit water at the outlet of the unit to a particular set temperature or range.
Therefore there remains a need in the technology associated with these instantaneous hot water heater units to provide an improved controlled switching arrangement of the ON and OFF sequencing of power to the heating element, such that water discharged from the unit can be sustained at a set temperature or range regardless of the inlet water temperature and without the pitfalls associated with the limiting factors connected with electro-mechanical switches and those related thereto discussed above.
It is an object of this invention to provide such a controlled arrangement to be able to sustain water in contact with a heating element at a set temperature or range within an instantaneous heater unit that is able to overcome the problems introduced precedingly.
Another of object this invention is to provide a means and method for controlling the temperature at the outlet of a hot water heater unit even in cases where the inlet temperature and water flow are varying and to do this proactively rather than relying on control responding to subsequent breaches of set temperature parameters for the instantaneous hot water heater unit sensed at the output.
Further objects and advantages of the invention will become apparent from a complete reading of the enclosed specification.